Systems of this kind are known, for example, from U.S. Pat. No. 7,325,507. This document discloses that the steering action, namely, the force exerted on the steering tiller or steering arm of the motor through the tiller, is generated manually by the operator. The system exerts only an action locking the motor or the rudder and, therefore, the steering tiller when a change in direction is not desired, that is, a change of route. This is advantageous since with very powerful motors or with considerable surfaces of the rudder, the force that has to be exerted on the steering tiller is considerable and has to be maintained at all times to avoid a spontaneous change in orientation of the rudder plate or motor that, in combination with the hydrodynamic behavior of the watercraft and of the motor. also with reference to the propeller shape, tends to reach the highest possible pivoting angle of the tiller and consequently of the rudder or motor. A situation of this kind is very dangerous. above all when cruise speed is high.
Besides such passive system, the document U.S. Pat. No. 6,715,438 discloses an active system where the steering control exerted on the tiller is translated into a control pulse changing the tiller angle corresponding to an actuator changing the rotation of the motor or rudder. The document, as the actuator, discloses a hydraulic actuator of the type known in hydraulic steering systems used in watercrafts both for moving the plates or rudders with inboard motors, and for moving motors when they are outboard motors.
In both documents the control member is composed of an end handle portion of the steering tiller having a portion mounted to swing according to an axis substantially parallel to the axis of rotation of the motor or plate of a rudder, such portion driving a valve opening a circuit supplying a pressurized fluid to one or both of the chambers of an actuating cylinder.
Document U.S. Pat. No. 7,325,507 discloses a circuit connecting the two chambers of a double-acting cylinder. A valve is opened and is mechanically controlled by the pivoting movement of the end portion of the steering tiller relative to the part associated to the motor, allowing a fluid to pass from one to the other chamber of the cylinder and therefore releasing the pivoting movement of the tiller.
If the rotation of the tiller is carried out by a non-manual force, the pivoting movement of the end portion of the steering tiller activates, still by way of a valve control, the passage of a pressurized fluid from one pressurized reservoir to the chamber of the cylinder, which, therefore, is moved with respect to the rod and moves the arm of the motor connected to the cylinder.
By bringing back the handle in the rest condition, the valve closes the passage and the movement is locked until the end portion of the steering tiller is again operated.
The choice of using the end portion of the steering tiller as the control actuating the valve is determined by the need of containing the pivoting movement of such portion with respect to the tiller. It is a vain pivoting movement meaning that it does not cause a corresponding rotation of the steering member of the boat. If such pivoting movement is too wide, the operator has the annoying feeling of uselessly rotating the tiller before effectively operating a steering movement. For this reason the arm of the member actuating the valve is as shorter as possible. If it was placed in the distal portion of the tiller the arm would be equal to the length of the tiller resulting in a very marked pivoting movement of its proximal end. The arc of a circumference is equal to the size of the angle in radians by its radius.
On the other hand such solution requires the valve to be placed in a remote position with respect to the cylinder and therefore it requires the presence of pipes connecting the valve and cylinder that have an extension at least equal to the length of the tiller. Long pipes involve continuous bending stresses with a high wear level thereof.
Moreover, in known modern steering tillers the tendency is to mount on the steering tiller a plurality of controls for different maneuvering functions of the boat, such as for example controls for motor tilt, controls for motor trim, controls for the motor reverse gear, for controlling the number of revolutions of the motor and so on. This makes spaces available on the steering tiller more and more limited and it is more and more difficult to avoid interferences between the several mechanisms housed in the tiller body, resulting in potential dangerous situations or maintenance difficulties.